Frying oils



United States Patent FRYING OILS Daniel Melnick, Teaneck, and Chester M. Goodiug, Westfield, N.J., assignors to Corn Products Company, a corporation of Delaware No Drawing. Original No. 2,874,055, dated February 17, 1959, Serial No. 496,592, March 24, 1955. Application for reissue July 29, 1959, Serial No. 832,871

6 Claims. (Cl. 99118) Matter enclosed in heavy brackets [I] appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to a novel class of frying oils or fats suitable for the commercial frying of foods such as potato chips, cereal snacks, fish sticks and related products and to a novel frying process employing these oils and fats. These new frying oils are vegetable oils which have been selectively hydrogenated to a particular range of iodine values. The new frying oils yield fried products having the characteristics of those fried in limpid oil, without the attendant disadvantages.

According to the prior art commercial frying of food products, two classes of oils or fats have been regularly employed by industry; these are either the limpid unhydrogenated oils or the frying shortenings. The former class includes limpid unhydrogenated cottonseed, corn or soybean oil, or combinations of such vegetable oils. The iodine number (Wijs) of these oils vary from 100 to 140. The same oils after hydrogenation to iodine numbers of 60 to 70, or animal fats of lower iodine number, represent the other class of frying oils or shortenings. The latter have a melting point (Wiley) of 104 to 115 F. (40-46" C.) and a setting or congealing point (according to the method of H. W. Vahlteich et al., U.S. Patent No. 2,047,530) of 82 to 88 F. (28-3l C.). Factors of eating quality of the fried product and flavor stability have motivated food processors to choose one type of fat over the other. Limpid peanut oil with an iodine number of from 90 to 95 is also used as a frying oil. For reasons which will be discussed below, peanut oil has been regarded as the best of all limpid frying oils but is available in limited amounts and at much higher cost than competitive limpid oils.

When fresh products, fried commercially in limpid oils, viz., potato chips, are eaten without modification in the home, they are preferred to those fried in shortenings or animal fats. Appearance and mouthing properties are superior and the full flavor of the fried products is released. Products fried in shortenings, on the other hand, are dry in appearance, hold poorly the added salt crystals, have dry eating qualities like those of a cracker, and the flavor of the product is masked to a significant degree by the high-melting fat which coats and penetrates the product; frying fats are absorbed in high concentrations of up to 40% by weight.

Commercially fried products, viz., fish sticks, frozen "ice during the period of retail sale and reheated prior to use, are also preferably fried in limpid oils. During freezer storage at l0 to 0 F., a frying shortening hardens on the surfaces of the fried food as a brittle opaque white coating and this objectionable appearance is maintained during the thawing-out period at room temperature. Furthermore, the individual fried units adhere strongly to each other because of the thick fat binder. When fried in limpid oils and then frozen, the products are not subject to the adverse criticisms associated with the use of shorteniugs.

One major disadvantage to the use of limpid unhydrogenated oils is lack of flavor stability of the resulting fried products. The limpid oils are readily susceptible to oxidative deterioration with the result that the fried products become rancid at a much earlier date than the same products fried in shortening. Peanut oil is the most stable of the limpid frying oils. This is apparent from the results shown in Table I below and obtained in the course of our research investigation of oil and fat products employed in regular commercial frying runs, wherein oil replenishment kept pace with oil removal by the product fried.

TABLE I Stability of prior commercial frying oils and potato chips.

fried in said oils 1 Active Oxygen Method of King et al., "Oil and Soap," vol. 10, page (1933), modified by Riemenschneider et al., "Oil and Soap," vol. 20, page 169 (1943). This method involves aeration of the oils and fats at 98 C. (208.5 F.) under standardized conditions until an organoleptlcally detected rancidity develops; this is associated with a peroxide value of milliequivalents per kilogram of fat; in the case of the limpid trying oils and 100 milliequivalents in the ease of the shortenings.

1 Objective flavor scorings conducted serially by a panel of ten judges, until a score of belowfair" was obtained. Products obtained after the frying oils were in an equilibrium state, i.e., when the ratio of fresh to heated oil in the frying vat is essentially constant as oil replenishment keeps pace with oil absorption by the product being fried.

As will be seen from Table I, the limpid vegetable oils and potato chips fried in them are characterized by low stability, whereas the shortenings and potato chips produced from them have significantly superior stability.

For the tests summarized in Table I above, a Macbeth fryer was employed. It held 1,750 pounds of oil and produced 250 pounds of fried potato chips per hour.

er rent-newsman atthe rate of 96 pounds per hour. Two varieties of potatoes; namely; Irish obblers and Kennibecs, were used in these tests. The potatoes were peeled in an abrasive-type machine, conveyed to a slicing machine, and the slices washed by alternate baths and sprays of water. The slices were dried by air blast and then conveyed to the oil-fried, steel Macbeth fryer. Oil temperature at the inlet was 350 F. Frying time varied from 2.5 to 3.0 minutes. Exit oil temperature was 385 F. The chips drained free of excess oil were salted during passage under a hopper-type, slotted rotary drum salter. At the end of each days operation, the hot oil was pumped from the fryer through a small filter press into a reservoir tank. The reservoir automatically supplied oil to the fryer during the daytime operations to keep the level of the oil in the fryer constant ($0.1 inch) and replace oil removed by the finished potato chips.

The prior art has attempted to blend shortenings with limpid frying oils to obtain flavor stability of the fried product intermediate between that noted when these types of'fats are employed individually. In other words, the goal has been to obtain the appearance and eating quality of products fried in limpid oil, and the flavor stability of products fried in shortening. Neither one of the two objectives has been realized. When the shortening component "amounts to more than 50 percent of the blend, appearance and eating quality of the fried foods are inrpaired. When the shortening component is less than 50 percent of the-blend, flavor stability of the fried products is practically no better than that noted when limpid vegetable oil is employed, viz., at most a one week's extension of the flavor life of potato chips stored at 95 F.

Despite such disappointing results, there is a widespreadv practice among commercial fryers to add shortening to limpid frying oil during the hot summer months in an attempt to improve the stability during this critical pe-' riod of shelf life.

The food frying industry has also attempted to add antioxidants, singly and in combinations, to permit the use of limpid unhydrogenated frying oils without sacrificing shelf life of the fried products. These additives include the true phenolic-type antioxidants, such as propyl gallate and butylated hydroxyanisole', and the metal-sequestering acid synergists, such as citric acid. These additives have limited stability at the high temperatures of frying (385 F.) with the result that the flavor life of the fried product is extended to only a small degree; at most by only 50 percent.

A second major disadvantage to the use of limpid unhydrogenated oils for frying foods is the susceptibility of these oils to thermal polymerization. Only the poly unsaturated fatty acids in the oils participate in thermal polymerization reactions. The oils of higher iodine number contain more of these polyunsaturated fatty acids than do oils of lower iodine value. Thus, unhydrogenatedsoybean oil contains up to 65 percent of linoleic plus linolnic acids (55%+10 while peanut oil contains up to 25 percent of linoleic acid. The values for corn and cottonseed oils are in between these two with about 45-'-5 5 percent linoleic acid and, as in the case of peanut oil, no linolenic acid. Frying shortenings contain no linolenic acid and very little linoleic acid, i.e., well under 8 percent.

When oils containing polyunsaturated fatty acids are heated for extended periods of time at high temperatures,- polymers are formed. The cyclized or branched monomers and the dimers are definitely toxic and should be avoided. As thermal polymerization proceeds, there is a progressive reduction in the iodine number of the oil,

since new G-C crosslinkages occur at the expense of the double bonds in the molecules involved. When food prod ucts are fried in limpid unhydrogenated vegetable-seed oils even with continuous addition of oil to the vat; to compensate for that absorbed, the iodine value of the oil e ome qs essively smal ert via, a d onin i.e. liaenum protect polyunsaturated fatty acids against oxidation cannot prevent them from participating in thermal polymerization reactions, since the latter also take place in an inert non-oxidizing atmosphere. The frying shortenings ex hibit no decrease in iodine value on continued use and therefore are free from thermal polymers.

It is an object of the present invention to provide frying oils which possess the desirable attributes of both limpid unhydrogenated vegetable-seed oils and of hydrogenated frying shortenings without the disadvantages associated with the use of each class of oil.

It is another object of the present invention to provide fried foods characterized by (a) having the appearance and eating quality of foods fried in limpid unhydrogenated oils, (b) having the flavor stability characteristic offfoods fried in hydrogenated shortenings, and (c) being free of undesirable thermal polymers.

I Additional objects will be apparent to those skilled in the art from the specification which follows. 1

The novel frying oils of the present invention are deodorized, selectively hydrogenated, vegetable-seed oils having an iodine value of from 75 to 94, a melting point of from to F., and a setting point of from 55 to 65 F. The source of the oil influences the ranges of constants somewhat. Thus, the values for frying fats produced from the more unsaturated vegetable oils, i.e., having an iodine value of and above, such ,as soybean and corn oils, after selective hydrogenation are.

preferably 82 to 94 for iodine value, 82 to 92 F. for melting point, and 55 to 65 F. for setting point. For frying fats produced from the more saturated vegetable oils, i.e., having an iodine value of less than 120, such as cottonseed and peanut oils, the ranges of values are preferably 75 to 92 for iodine value, .85 to 95 F for melting point, and 55 to '65 F; for setting point. This range of setting point values is the common denominator for all the new frying oils of the invention.

The established methods for the determination of the setting (congealing) point of hydrogenated oils are not applicable to the new frying oils. As employed indescribing the frying oils of thisinvention this value is deter. mined by first pre-chilling the oil to 555 F.in a 32- 4l F. water bath and then transferring it to a 32'4'1 F.

of the conventional limpid frying oils had to be developed in order to differentiate more clearly these oils of the prior art from those of the present invention. The procedure calls for the pre-chilling of the limpid oils to 5' to 5'' F. in an acetone-solid carbon dioxide bath with slow uniform agitation until the first turbidity develops, transference of the tube containing the oil to an air bath at 5 to 5 F. and recording the highest temperature as the setting point. In determining the melting points of these same limpid frying oils, the Wiley method also had to be modified. The oil is cast as a solid disc on solid carbon dioxide, and the disc added to a melting point tube containing a 50:50 glycerine to water solution as the bottom layer and isopropanol as the top layer. Thetemperattire of the acetone-solid carbon dioxide bath is gradually raised by adding more acetone, the latter be; ing at about 75 F. The same end-point in the standard Wiley procedure, the temperature at which the disc at the interphase becomes .an elastic sphere, is recorded as the melting point. v r 7 The new frying oils of the present invention are the that sharasteri sd by a reductiqn in linolei a i can tent of from 50% to 90% of the content of the original unhydrogenated oil, but without any significant increase in saturated fatty acid content as determined by the method of test to be discussed below. Thus, in the case of highly unsaturated or polyunsaturated fatty acids to the mono-saturated fatty acids, but in the course of this addition of hydrogen at the double bonds there are formed in appreciable concentrations fatty acid isomers with the new frying oils prepared by selectively hydrogenating physical and chemical properties different from the natoils originally having a linoleic acid content of about urally-occuring unsaturated fatty acid. Conditions of hy- 50%, such as cottonseed oil, the linoleic acid content drogenation will determine in large measure the relative varies from 15% to 25% (a reduction of from about quantities of the fatty acid isomers in a fat. Under se- 50% to 70%) and the saturated fatty acid content is no lective conditions of hydrogenation there occurs prefgreater than that of the original unhydrogenated oil (not erential hydrogenation of the fatty acids containing acmore than 25 Also in the case of the new frying oils tive methylene groups (linoleic) in preference to acids prepared from unhydrogenated oils having a polyunsatdevoid of such groups (oleic). It therefore follows that urated fatty acid content of above 50%, such as soybean in selective hydrogenations, with greater opportunities oil, the saturated fatty acid content is not increased despite provided for the preferential hydrogenation of the polya 70% to 90% reduction in linoleic acid content (to unsaturated fatty acids, there occurs to a greater degree 5%, to 15%) and a 90% to 100% reduction in linolenic the development of fatty acid isomers and to a much acid content (to not more than 1%). lesser degree the development of saturated fatty acids.

The present invention finds its greatest applicability in There are several conditions which have a bearing upproducing those selectively hydrogenated vegetable-seed on whether the hydrogenation shall be non-selective or oils which originally possessed a high linoleic acid conselective in character, and those skilled in the art are tent, lin leic and content In excess of 30%. Exfamiliar with them. In general it may be said that the amples of vegetable oils having such an initial linoleic lower the pressure conditions, the higher the temperature, acid content are: corn, C tt s d, y P PPY the lesser the agitation and the more active the catalyst, sesame, sunflower, rice-bran, etc. the more selective the character of the hydrogenation is Examples of the new class of frying OllS of this rnvenlikely to b While ea h of these factors, as well as tion are given in Table II below. For the purpose of others with which those skilled in the art are familiar, comparison, the properties of fatty acid composition [of] plays a part in determining the character of the hydroand the oils and shortenings used by the frying industries genation, the condition which plays the role of primary in accordance with the teachings of the prior art are also importance in controlling the type or character of the listed in Table II. Table II follows: hydrogenation 1s temperature. The other conditions,

TABLE II Novel frying oils of the presentinvention in reference to trying oils used by the prior art Fatty acid content A.O.M. Example Class 1 Iodine M.P., S.P., value, value F. F. Lin- Lln- Oleic, Satuhours 1 olenic, olelc, percent rated,

percent percent percent Ref. 12.... Lirnpid unhydrogenated CSOL. 109.0 57.0 30.2 0.0 49.6 21.3 24.7 12 Ref.B Frying CSO shortening 60.6 103.3 84.4 0.0 2.1 63.1 30.4 90 59.4 109.0 86.9 0.0 6.8 52.5 36.3 60 84.9 90.7 59.5 0.0 18.6 57.0 20.0 30 81. 2 92.0 63. 0 0. 0 15. 8 58. 5 21.3 as 91.0 88.3 56.3 0.0 25.2 50.8 19.6 26 85. 4 91.8 63. 0 0. 0 18. 9 57. 0 19. 7 94 Limpid unhydrogenated SBO 132.2 24.0 11.3 6.8 52.6 23.8 12.4 8 Ref. 15.-.. Frying SBO shortening 67. 2 106.9 89.4 0.0 0. 0 74. 8 20. 8 210 69. 5 114. a B4. 6 0. 0 4. 3 68.6 22. 7 120 88.5 85.5 58.5 0.5 10.4 76.0 8.7 60 86.0 91.0 59.2 0.2 8.9 77.1 9.4 75 89.8 83.5 56.7 0.5 12.1 74.0 9.0 57 83.3 83.3 59.5 0.1 6.4 79.5 9.6 92 122. 3 27. 0 12. 2 0. 0 51. 4 32. 6 11.6 10 NovelFrying 87.2 87.8 59.1 0.0 12.1 72.7 10.8 51 Ref. Limpid unhydrogenated PNo- 93.4 59.0 37.8 0.0 25.1 53.5 17.0 24 1o Novel frying PNO 76.4 86.6 58.0 0.0 7.8 69.4 18.4 55

1 0S0=cottonseed oil; SBO=soybean oil; O0=coru oil; PNO=peanut 011.

2 As defined in Table I.

Reference oils A, D, G and H shown in Table II above 55 such as pressure, agitation and catalyst activity, are of arethe limpid vegetable-seed oils [comployed] employed in accordance with prior art practices by those who prefer to make fried products more acceptable in appearance and eating quality even though their use requires a sacrifice in resistance to thermal polymerization and in flavor stability of the fried products. Reference oils B and E are the shortenings obtained following selective hydrogenation of the limpid oils, while reference oils C and F are those shortenings obtained following nonselective hydrogenation of the limpid oils. The latter method of hydrogenation gives products of higher linoleic acid content, reduced oleic acid content, and higher saturated fatty acid content, and of lower stability than that which obtains following selective hydrogenation.

The new class of frying oils of the present invention, including the oils of Examples 1 through 10 of Table II, is produced by selectively hydrogenating limpid'vegetable oils to particular ranges of critical values. In the hydro g'enation of vegetable oils in rn'akinga frying shortening, there occurs not only a step-wise conversion of the more much lesser importance. We have observed that, generally speaking, a temperature of 260 F. may be said to be the dividing point between selective and non-selective conditions. More specifically, at hydrogenation temperatures below 250 F. the hydrogenation is likely to be non-selective in character, while at temperatures above 260 F. the hydrogenation is likely to be selective. Naturally, the lower the temperature, the more non-selective will be the hydrogenation; while the higher the temperature, the more selective it will be. We contemplate employing hydrogenation temperatures in excess of 250 F. and preferably between 300 and 350 F.

Demonstrating the process according to the present invention of selective hydrogenation of limpid vegetable oils are the examples below. These examples are merely illustrative of the process and other conditions which are equivalent to those shown may be employed. To pro ,vide a better comparison between oils, the selective hydrogenation conditions were substantially identical in' eachcase.

. EXAMPLES .Iin each ofExamplesl through 10 oi Table nova, limpid vegetable oils, which had been alkali-refined, were employed as the starting materials. amples 1-4 the starting material was the limpid unhydrogenatedcottonseed oil of reference A. Examples 5-8 employed the limpid unhydrogenated soybean oil of reference D. Examples 9 and 10 employed the limpid unhydrogenated oils of references G and H, respectively.

Each of the limpid unhydrogenated starting oils was pumped in a quantity of 20,000 pounds into separate hydrogenatio n vessels. About 0.1% (based upon nickel content of the catalyst) of a ni'clgel catalyst kno wn as Ruferts catalyst (described in US. Patent No. 2,424;811) was added to each oil. The temperature of the mixture was raised in each case to between about 270- F. and 300 F. and upon subjecting each reaction mixture to hydrogen gas at a pressure maintained at about 20 pounds per square inch, the temperature was increased to 300 350 F. The hydrogenation was permittedto continue with agitation of the reaction mixture until the setting point, melting point and iodine value in each case corresponding to those listed for the appropriate example in Table II above. The resulting hydrogenated oils were then filtered to remove the catalyst and finally deodorized by the usual high-vacuum steam t1'ea:tment.-

In the case of Ex- In Table II above the fatty acid contents of the oils were determined as follows: Polyunsaturated fatty acid composition was determined according to the spectrophotometric method of Brice and associates, Oil and Soap, vol. 22, page 219 (1945). Oleic acid content was based upon the iodine value of the oil after correcting for the polyunsaturated fatty acids present, and saturated tion at the latter. ,However, the spectrophotometric method, employed here, is suificiently accurate and reproducible to permit us to define with reasonable precision the fatty acids distribution of the frying oils of the present invention.

In Table III below are presented data showing that th blending operations of the prior art and as practiced inthe frying industries, whereby a limpid unhydrogenated oil 'i'sinixed with afr'ying shortening, are inadequate to match the vperforrnance of the novel frying oils of this invention. A :50 blend of limpid cottonseed oil with a cottonseed oil shortening (obtained by selective or by non-selective hydrogenation) yields an oil with an iodine number falling in the middle of the range of iodine values for the new cottonseed frying oils of the present invention. .But from this point on, similarity between the blends and our novel frying oils ceases. The blends of the prior art have much higher melting points, very much higher setting points, and much more linoleic and saturated fatty acid contents. In resistance to oxidative deterioration the blends are very much inferior to the novel frying oils of the present invention. The same pattern is apparent when the source of oils is soybeans. Decreasing the ratio of limpid oil to frying shortening to improve the stability of the oil blends is no solution'to the problem since the blends then take on more and more the undesirable physical properties of a shortening. As the blends are formulated, they are already undesirable in this respect. Table III follows:

Failure of blends of duplicate the new class of frying mm in the frying oils of the prior art to oils of the present Invention Fatty acid content A.0.M. Frying oil I Iodine M.P., .S.P., value, value F. F. ,Lin- Linolelc, Oleic, Satuhours olenlc, percent percent rated, percent percent 50:50 blend of limpid CS0 and CS0 shortening (refs. A+B of Table II) 84. 9 98. 7 74.0 0.0 26.2 41.8 27.4 16 50:50 blend of lirnpld CEO and CS0 shorten- .ing (refs. A-I-G of Table II) ..1. 84. 5 100.2 75.8 0.0 28. 2 37. 3 30. 1 15. New trying CSO of the present invention-.- -92 -95 55-05 0.0 15-25 50-60 19-22 25 40 33267-blend of limpid SBO'and SBO shortening (refs. D+E of Table II 88.9 100.6 80.0 2 2 17.3 57.5 18.6 24 33:67 blend of limpld S and SEC shortening (refs. D-I-F of Table II) 89. 9 102.0 76.4 2.2 20.2 52. 7 20.5 20 New trying SBO of the present inventlon. 82-94 1 82-92 55-65 0-1 5-15 70-80 8-12 50-100 1 CSO=cottonseed oil; SBO=soybean oil. 1 As defined in Table 1.

fatty acid content was'calculated by (inference, Beadle Oil and Soap, vol. 23, page (1946). This method, when applied to hydrogenated oils, tends to overestimate oleic acid content and underestimate saturated fatty acid content. During hydrogenation, the middle double bond in linolenic acid may be hydrogenated and migration of double bonds may also occur. Isomers can be so formed which do not respond to the spectrophotometric method for the polyunsaturated fatty acids, i.e., polyunsaturated fatty acids (isolinoleic acids) are produced with double bonds so far removed that conjugation cannot .be effected by the alkali treatment prior.- to .spectrophotometric measurement. Such .linoleic acid isomers react like twice 75 -In Table IV below are tabulated the organoleptic qualities and stability of potato chips fried in the oils of the present invention and in blends of oils of the two classes as employed by the prior art. It will be noted that chips,

fried in the oils blends take on all the undesirable properties (appearance and eating qualities) of chips fried.

in shortenings and the undesirable lack of stability of chips fried in limpid unhydrogenated oils (compare:

procedure described above in connection with Table I, except that the frying oils were those listed in the table. Table IV follows:

TABLE 1v From the data presented in Table V above we have concluded that free fatty acid development in the novel frying oils of the present invention occurs at a slower Organoleptic qualities and stability of potato chips fried in the oils of the present invention and in blends of oils of the two classes as employed by the prior art Properties of the potato chips Iodine Frying oil I value Flavor- Appearance and eating qualities life 1 at 95 F., weeks Example 1, new frying S0 (see Table II). 84.9 Liquid oil film on surface good salt adherence, good 8 mouthing properties, full aver release. 50:50 blend of limpid CS0 and CS0 shorten- 84.9 Dry in appearance, poor salt adherence, dry mouthing 3 ing (Refs. .A-i-B of Table Ill. roperties, flavor mufied. Example 5, new frying SBO (see Table II) 8S. L quid oil film on surface, good salt adherence, good 7 mouthing properties, full flavor release. 33:57 blend of limpid SBO and S130 shorten- 88.9 Dry in appearance, poor salt adherence, dry mouthing 1.5

ing (Refs. D+E of Table II). properties flavor muffed.

1 GSO=cottouseed oil; SBO=soybean oil.

I Objective flavor scorings conducted serially by a panel of judges, until a score of fair was obtained. Products obtained after the frying oil had attained an equilibrium state.

During the course of our investigation, the resistance to thermal polymerization of the novel frying oils of the present invention was determined. Since the commercial frying of potato chips was found to produce only a minimum of free fatty acids, another system which produces larger amounts of free fatty acids was employed for the tests. It was found that in the commercial frying of breaded fish sticks or French-fried potatoes there is a progressive increase in free fatty acid content with continuous frying until values as high as 10.0% are sometimes obtained. Consequently, it was decided to conduct our studies by frying breaded fish sticks as the tcstsystem to follow thermal polymerization changes.

The frying system used for these thermal polymerization rate studies contained 3,250 pounds of oil which was maintained at a temperature of about 385 to 390 F. The level in the fryer was maintained constant by continuously feeding in fresh oil, about 260 pounds per hour, to replenish that absorbed by the fried fish sticks, which were fried for about 50 seconds. The oil in part was passed during the continuous operation through a filter, containing filter aid plus fullers earth, to remove fine bread crumbs. For reasons mentioned hereinabove a drop in iodine value was considered as an indication of the extent of thermal polymerization changes. The results of this study comparing a novel cottonseed oil frying fat according to the present invention with an unhydrogenated limpid corn oil are sumarized in Table V. Table V follows:

TABLE V Thermal polymerization of prior art frying oils and the novel frying oils of the present invention in frying of breaded fish sticks Unhydrogenated Cottonseed frying oil limpid corn frying oil according to the present invention Frying time, hours Free fatty Iodine Free fatty Iodine acids, pervalue acids, pervalue cent cent polymerization changes occur when the novel frying oils of this invention are employed, whereas with limpid unhydrogenated corn oil such changes do occur (progressive decrease in iodine value). The novel frying cottonseed oil used in this particular study originally contained 16.8% linoleic acid, while the limpid unhydrogenated corn oil contained at the start 51.4% linoleic acid. One would then expect thermal polymerization to occur in this oil also but to about one-third the degree, i.e., a decrease of about 6 to 7 in iodine value after the 225 hours of frying. Such did not occur. It now appears from our results that thermal polymerization changes in a frying oil are dependent upon a particular minimal concentration of polyunsaturated fatty acids in the oil and the possibility of such undesirable changes occurring increases at a geometric rate as the concentration of polyunsaturated fatty acids in the oil increases.

The novel frying oils of this invention may be oils from one source, viz., cottonseed or soybean, selectively hydrogenated to within the limits set forth above, or blends of oils from two or more sources selectively hydrogenated to within the prescribed limits, or blends of the new frying oils themselves.

Antioxidants of the phenolic type (such as butylated hydroxyanisole) with or without acid synergists (such as citric acid or mono-esters of citric acid in accordance with US. Patent No. 2,485,632 of H. W. Vahlteich et al.) may also be added to the new frying oils for increasing the flavor life of both the novel frying oils and the products fried therein.

As employed herein, and in the appended claims, the terms frying oil and vegetable-seed oil are intended to include any vegetable fat which has an iodine value, melting point [seting] setting point within the ranges specified for the oils of the present invention.

The terms and expressions which we have employed are used as terms of description and not of limitation and we have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. A novel frying oil [comprising] consisting essentially of a deodorized, hydrogenated vegetable-seed oil having an iodine value of from 75 to 94, a melting point iron 80 to 95 F., and a setting point of from n 2, A novl oil [com risin consisting essentifiily of a deodorized, hydrogenated vegetable-seed oil having an iodine value of from 82 to 94, a melting point of from 82 to 92 F., and a setting point of from 55 to F., and having a polyunsaturated acid content which has been reduced from 50% to.90% of that of the original [unhydrogented] unhydrogenated oil from which it is produced but-having no greater saturated fatty acid content than the original oil.

3. A novel frying oil [comprising] consisting essentially of a deodorized, hydrogenated vegetable-seed oil having an iodine value of from to 92, a ine'lting point of from to 95 F., and a setting point of from 55 to 65 F., and having a polyunsaturated acid content which has been reduced from 50% to ofthat of the original unhydrogenated oil frorn which it is produced but having no greater saturated fatty acid content than the original oil. r

4. A novel frying oil [comprising] consisting essentially of a deodorized, hydrogenated cottonseed oil'having an iodine value of froiii 80 to 92, a melting iioint of from 85 to F., a setting point of from .55 to 65 F a linoleic acid content of from 15% to 25%, and a saturated fatty acid content of not more than about 25%. j

' 5. A novel frying oil [comprising] consisting ssentinlly of a deodorized, hydrogenated soybean oil having an iodine value'of from 82 to 94, a melting point of from 82 to 92 F., a setting point of frozn 55 to 65 F., a. linoleiiic acid content of not more than 1%, a linoleic acid camem'or frorn 5% to 15%, and a saturated fatty acid content of not more than about 13% 6, A frying oil [comprising]. cpnsisting essentially d a deodorized hydrogenated vegetable seed oil havingari iodine value of about 76.4 to 88.5, a melting point as about 83.3 to 920 F., a setting point of about 58 to 63 F., a linoleic acid content of about 6.4 to 18.9%, an oieic acid contentof about 57.0 to 79.5%, and a saturated acid content of about 8.7 to 21.3%.

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